Process for production of 1-amino-2-sulfo-4-brom-anthraquinone



Patented May 4, 1948 PROCESS FOR PRODUCTION OF 1-AMINO-2- SULFO- l-BROM-ANTHRAQUINONE.

George W. Seymour, Victor S. Salvin, and Walter R. Edwards, Cumberland, Md., assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application September 13, 1944, Serial No. 553,960

4 Claims. (01. 260-4371 This invention relates to dyestuif intermediates and relates more particularly to an improved process for the production of l-amino-Z-sulfoibrom-anthraquinone. 7

An object of this invention is to provide an improved process for the production of l-amino- 2 sulfo 4 brom anthraquinone of increased purity and in improved yield.

Other objects of this invention will appear from the following detailed description.

The dyestuff intermediate 1-amino-2-sulfo-4- the yield of the desired intermediate and their presence seriously interferes with the production of dyestuffs of consistently satisfactory purity and fastness properties from the valuable 1- amino 2 sulfo 4 brom-anthraquinone intermediate.

We have now discovered that l-amino-2-sulfo- 4-brom-anthraquinone may be prepared in increased purity and improved yield from l-amino- 2-sulfo-anthraquinone by a novel bromination procedure. In accordance with the process of our invention, these advantages are achieved if 1-amino-2-sulfo-anthraquinone is brominated'in aqueous acid solution at a relatively low temperature while maintaining a salt concentration in the solution just high enough to cause the 1-amino-2- sulfo-4-brom-anthraquinone to precipitate from solution as it is formed without precipitating the unreacted l-amino-2-sulfo-anthraquinone. By causing the 1 amino 2 sulfo-4-brom-anthraquinone to precipitate as formed, side reactions are minimized and a maximum yield of the desired brominated intermediate is obtained. The 1-amino-2-sulfo-4-bromanthraquinone obtained in accordance with our process is of very high purity and yields of over 85% may be consistently obtained.

The concentration of the 1-amino-2-sulfoanthraquinone in the aqueous solution during bromination is preferably from about 2 to 4% by weight, but optimum results are achieved during bromination employing an aqueous solution of 2 1-amino-2-sulfo-anthraquinone in a concentration of about 2.5%. Bromination is efiected by adding bromine in the form of a solution in dilute hydrochloric acid to the aqueous solution of lamino-2-sulfo-anthraquinone. The bromine is preferably added as a 10% solution in aqueous hydrochloric acid of 15 to 20% concentration. The addition of a 10% molar excess of bro-mine is usually suflicient to make up any loss because of any dibromination which takes place. I

The temperature during bromlnation may be held at from --2 to 2 C. but optimum results are achieved if bromination is effected at about To ensure immediate precipitation of the 1- amino-2-sulfo-4-brom-anthraquinone as formed and to avoid the side reactions which form undesired by-p'roducts, the salt concentration and the acidity of the solution must be closely controlled. Salts which may be'employed, for example, are sodium chloride, potassium chloride or sodium sulfate, but we prefer to empl-oysodium chloride as the salting out agent. Thus, when brominating at 0 C. the concentration of the sodium chloride should be maintained at. about 2% on the weight of the reaction mixture, whilethe concentration of mineral acid during bromination, which acid is preferably hydrochloric acid, should be about 2 to 4% by weight. Sulfuric acid may also be employed to maintain the desired acidity. Increased salt concentration tends to cause precipitation of 'unreacted 1-amino-2- sulfo-anthraquinone which is, of course; quite undesirable. Furthermore, by maintaining the acid concentration within the above limits the tendency of the bromine to oxidize the amino group to the hydroxy group with the resultant formation of 1-hydroxy-2-sulfo-4-brom-anthraquinone is greatly minimized.

After the addition of the desired quantity of the acid solution of bromine to the cooled aqueous solution of 1 amino 2 sulfo anthraquinone, which addition is usually effected over the course of 5 to 8 hours, the reaction is allowed to continue with agitation until all the bromine present has reacted completely, the temperature being maintained at -2 to 2 C. during reaction. This point, i. e. complete reaction, is usually reached after about one hour when a test for bromine should be negative. The entire reaction mixture is then added to an approximately equal volume of hot water and the whole is heated to to C. to dissolve the precipitated 1-amino-2-sulfo-4- brom-anthraquinone an'd'leave undissolved any 1-amino-2,4-dibrom-anthraquinone which has and may be filtered from solution. Any unreacted -amino-2-sulfo-anthraquinone may be salted out of the filtrate and recycled in the process.

In order further to illustrate our-invention, but Without being limited thereto, the following example is given:

Example 100 parts by weight of pure 1-amino-2-sulfoanthraquinone are dissolved in 4000 parts by weight of water at a temperature of 80 C. and the hot solution is filtered to remove insoluble matter. To this 2.5% solution of l-amino-Z- sulfo-anthraquinone are added'80 parts by weight of sodium chloride to make the salt concentration 2%, and then 254 parts by weight of hydrochloric acid (sp. grav. 1.18) are added and the whole cooled with stirring to C.

The bromine solution for bromination is prepared by adding 54 parts by Weight of bromine to a solution of 241 parts by weight of hydrochloric acid (sp. grav. 1.18) in 236 parts by weight of water with agitation and when the bromine addition is completed the solution is cooled to 0 C. Bromination is efiected by adding the aqueous hydrochloric acid solution of bromine to the cooled solution of 1 amino -.2'-.su1fo -'anthraquinone over the course of live hours. During the addition of the bromine, the 1-amino-2- sulfo-4-brom-anthraquinone precipitates from solution as it is formed. After all of the bromine has been added, the reaction is allowed to continue for one hour with stirring at 0 C. At this point a test for bromine should be negative.

The reaction mixture is then poured into 4650 parts byweight of water at 25 C. and the whole is heated to 80 C. Solution is complete except for any 1 amino 2,4-dibromanthraquinone formed. The latter is filtered off, Washed with 500 parts by weight of water at 80 'C. and the filtrates are combined.

The desired intermediate 1-amino-2-sulfo-4- brom-anthraquinone is precipitated from the combined filtrates by adding 400 parts by weight of sodium chloride and 153 parts by weight of hydrochloric acid (sp. grav. 1.18) thereto and cooling the solution obtained. The concentration ofsodium chloride in the solution during precipitation is 5% while the hydrochloric acid concentration is 2%. The 1-amino-2-sulfo-4-bromanthraquinone precipitates as a flocculent precipitate during cooling and is filtered off and washed with about 1000 parts by Weight of neutral 4% sodium chloride solution.

Unreacted 1 amino 2 sulfo-anthraquinone maybe recovered from the combined filtrate and wash liquor by adding 1620 parts by weight of sodium chloride thereto and saltingthe 1amino- 2-sulfo-anthraquinone from solution. This com pound may then be recycled in the process. An overall yield of 83 to 86% of 1-amino-2-sulfo-4- brom-anthraquinone is obtained after recycling the unreacted 1-amino-2-sulfo-anthraquinone.

Our novel process enables 1-amino-2-sulfo-4- brom-anthraquinone to be obtained in improved yield and in a high state of purity thus enabling dyestufis of consistently satisfactory color value and fastness properties .to be obtained therefrom.

It is to be understood that the foregoing detailed description is given merely by Way of illustration and that many variations may be made therein without departing from the spirit of our invention.

- Having described our invention, what we desire to secure by Letters Patent is:

1. Process for the production of l-amino-Z- sulfo-4-brom-anthraquinone, which comprises brominating with a solution of bromine in aqueous mineral acid 1-amino-2-sulfo-anthraquinone dissolved in an aqueous mineral acid solution containing an inorganic salt, the concentration of said mineral acid being maintained, during bromination, at 2 to 4% by weight of the reaction mixture and that of said inorganic salt at 2 to 3% by weight of the reaction mixture, and the bromination'reaction being carried out at a temperature of 2 to 2 0., whereby the l-amino-2-sulfo-4-bromanthraquinone as formed is precipitated from solution.

2. Process for the production of l-amino-Z- sulfo-4-brom-anthraquinone, which comprises brominating with a solution of bromine in aqueous hydrochloric acid l-amino-Z-sulfoanthraquinone dissolved in an aqueous hydrochloric acid solution containing sodium chloride, the concentration of said hydrochloric acid being maintained, during bromination, at 2 to 4% by weight of the reaction mixtureand that of said sodium chloride at 2 to 3% by Weight of the reaction mixture, and the brominaticn reaction being carried out at a temperature of ,2 .to 22 (3., whereby the 1.-amino-2-sulfo-.4-bromanthraquinone as formed is precipitated from solution.

3. Process for the production of 1-aminc-2- sulfo-4-brom-anthraquinone, which comprises brominating with a solution of bromine in aqueous hydrochloric acid 1-amino-2-sulfoanthraquinone dissolved in an aqueous hydrochloric acid solution containing sodium chloride, the concentration of said l-amino-Z-sulfoanthraquinone being about 2 to 4% by weight and the concentration of said hydrochloric acid being maintained, during bromiiiation, at 2 to 4% by weight of the reaction mixture and that of. said sodium chloride at 2 to 3% by weight of the reaction mixture, and the bromination reaction being carried out at a temperature of 2 to 2C., whereby the 1-amino-2-sulfc-4-bromanthraquinone as formed is precipitated from solution.

4. Process for the production of 1-amino-2- sulro-4-brom-anthraquinone, which comprises brominating with a solution of bromine in aqueous hydrochloric acid l-amino-Z-sulfoanthraquinone dissolved in an aqueous hydrochloric acid solutioncontaining sodium chloride, the concentration of said l-amino-2-sulfoe anthraquinone being about 2 to 4% by weight and the concentration of said hydrochloric acid being maintained, during bromination, at 2 to 4% by weight of the reaction mixture and that of said sodium chloride at 2 to 3% by Weight of the reaction mixture, and the bromination reaction being carried out at a temperature of 2 to 2 0., whereby the l-amin'o-2- with water and heating to dissolve the precipitated 1-amino-2-sulfa-4-bromanthraquinone filtering cit undissolved material, adding sodium 6 chloride to the hot filtrate, cooling to precipitate TED the 1-amino-2-su1Io-4-brom-anthraquinone and 1 UNI STATES PATENTS separating the precipitate from the liquid. gg Name 2 GEORGE SEYMOUR 2,3 a Scott 3 VICTOR SALVIN, 5 FOREIGN PATENTS WALTER R. EDWARDS. Number Country t 5,459 Great Britain 190 REFERENCES CITED 146,691 Germany Nov. 9, 1903 The following references are of record in the 263,395 Germany Aug. 9, 1913 10 file of this patent: 

